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    public partial class MainWindow : Window
    {
        #region APIs
 
        [DllImport("user32.dll")]
        public static extern bool GetCursorPos(out Point pt);
 
        [DllImport("user32.dll", EntryPoint = "WindowFromPoint", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern IntPtr WindowFromPoint(Point pt);
 
        [DllImport("user32.dll", EntryPoint = "SendMessageW")]
        public static extern int SendMessageW([InAttribute] System.IntPtr hWnd, int Msg, int wParam, IntPtr lParam);
        public const int EM_GETSEL = 0x00B0;
 
        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        internal static extern IntPtr GetForegroundWindow();
 
        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        internal static extern IntPtr GetFocus();
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        internal static extern int GetWindowThreadProcessId(int handle, out int processId);
 
        [DllImport("user32", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        internal static extern int AttachThreadInput(int idAttach, int idAttachTo, bool fAttach);
        [DllImport("kernel32.dll")]
        internal static extern int GetCurrentThreadId();
 
        [DllImport("user32", CharSet = CharSet.Auto, SetLastError = true)]
        internal static extern int GetWindowText(IntPtr hWnd, [Out, MarshalAs(UnmanagedType.LPTStr)] StringBuilder lpString, int nMaxCount);
 
        #endregion
 
        private DispatcherTimer timer = new DispatcherTimer();
 
        public MainWindow()
        {
            InitializeComponent();
 
            timer.Interval = TimeSpan.FromSeconds(2);
            timer.Tick += timer_Tick;
            timer.Start();
        }
 
        void timer_Tick(object sender, EventArgs e)
        {
            try
            {
                MultiLineTextBox.Text = GetTextFromFocusedControl();
            }
            catch (Exception exp)
            {
                MultiLineTextBox.Text += exp.Message;
            }
        }
 
        //Get the text of the focused control
        private string GetTextFromFocusedControl()
        {
            try
            {
                int activeWinPtr = GetForegroundWindow().ToInt32();
                int activeThreadId = 0, processId;
                activeThreadId = GetWindowThreadProcessId(activeWinPtr, out processId);
                int currentThreadId = GetCurrentThreadId();
                if (activeThreadId != currentThreadId)
                    AttachThreadInput(activeThreadId, currentThreadId, true);
                IntPtr activeCtrlId = GetFocus();
 
                return GetText(activeCtrlId);
            }
            catch (Exception exp)
            {
                return exp.Message;
            }
        }
 
        //Get the text of a control with its handle
        private string GetText(IntPtr handle)
        {
            int maxLength = 512;
            IntPtr buffer = Marshal.AllocHGlobal((maxLength + 1) * 2);
            SendMessageW(handle, EM_GETSEL, maxLength, buffer);
            string w = Marshal.PtrToStringUni(buffer);
            Marshal.FreeHGlobal(buffer);
            return w;
        }
    }

SendMessageW(handle, WM_GETTEXT, maxLength, buffer);

        private void SendCtrlC(IntPtr hWnd)
        {
            uint KEYEVENTF_KEYUP = 2;
            byte VK_CONTROL = 0x11;
            
            SetForegroundWindow(hWnd);
            keybd_event(VK_CONTROL, 0, 0, 0);
            keybd_event(0x43, 0, 0, 0);
            keybd_event(0x43, 0, KEYEVENTF_KEYUP, 0);
            keybd_event(VK_CONTROL, 0, KEYEVENTF_KEYUP, 0);
 
        }

        public string GetClipboardText()
        {
 
            string returnText = "";
            if (Clipboard.ContainsText(TextDataFormat.Text))
            {
                returnText = Clipboard.GetText(TextDataFormat.Text);
            }
 
            return returnText;
        }

            string selectedText = "";
 
            IntPtr hWnd = GetForegroundWindow();
 
            uint processId;
            uint activeThreadId = GetWindowThreadProcessId(hWnd, out processId);
 
            Process p = Process.GetProcessById((int)processId);
            appName = p.ProcessName;
 
            uint currentThreadId = GetCurrentThreadId();
            AttachThreadInput(activeThreadId, currentThreadId, true);
            focusedHandle = GetFocusWindow.GetFocusedHandle();
            SendCtrlC(focusedHandle);
            AttachThreadInput(activeThreadId, currentThreadId, false);
 
            selectedText = GetClipboardText();

[DllImport("user32.dll", SetLastError = true)]
static extern void keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);
 
public const int KEYEVENTF_EXTENDEDKEY = 0x0001; //Key down flag
public const int KEYEVENTF_KEYUP = 0x0002; //Key up flag
public const int VK_LCONTROL = 0xA2; //Left Control key code
public const int A = 0x41; //A Control key code
public const int C = 0x43; //A Control key code
 
public static void PressKeys()
{
            keybd_event((byte)VK_LCONTROL, 0, KEYEVENTF_EXTENDEDKEY, 0);
            keybd_event((byte)C, 0, KEYEVENTF_EXTENDEDKEY, 0);
            keybd_event((byte)C, 0, KEYEVENTF_KEYUP, 0);
            keybd_event((byte)VK_LCONTROL, 0, KEYEVENTF_KEYUP, 0);
}